marine life in Cornwall

Tag Archives: Polyides rotundus

Rumours had it that the viz was great at the North Coast last weekend, and as it was pretty bad at the south Coast, I found some time to drive up to St. Agnes (buying new fins on the way) with the fisheye lens+dome. I was not disappointed: look at that blue sea! The water was clear, the sand was white and the seaweeds were waving on the rock faces. I saw flounder, mullet (thicklipped and red), seabass, sand eels, corkwing wrasse, sand smelt and most interestingly: weeverfish. Swimming above the sand with yellow fins and burying themselves so only the eyes are visible. I saw one half a meter deep on the beach, so it is advisable to wear surfshoes (see here). Unfortunately I could not get a good photo. I tried to take photos with the strobe but that did not really work so all photos here are natural light, trading off ISO, shutterspeed and depth of field to get the right exposure. There were Blue jellyfish around (small, 2-4 inches), and I tried to shoot them over-under but that was a bit too ambitious. Some easier shots instead. I hope to find some big Barrel jellyfish in the coming weeks, as they will be a lot easier to shoot!As the fish proved a bit too fast, and the over-unders a bit too difficult, I tried to take some shots of seaweeds instead. Although I mainly knew it from more sheltered locations, there was quite a bit of Mermaid’s tresses Chorda filum on this exposed coast. There was a lot of discoid forkweek Polyides rotundus on the sand but also on the rocks, and often covered in Falkenbergia. Other species that were abundant were Hairy sandweed Cladostephus spongiosus and Desmarestia ligulata. Hope to return soon!

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Above the spot where I have been snorkeling all year at Tunnel Beach, between Castle- and Gylly Beach, in Falmouth (Pendennis Castle can be seen in the background). The best time to snorkel is before low tide, as when the tide comes in the viz gets worse. I try to aim for 50-100 cm above the low tide mark which is really shallow. This area is not a real rock pool but rather a gravelly zone between the rock pools proper and the kelp forest which begins past the last row of rocks on the photo. Last week I went snorkelling three times but only last Thursday had decent viz. The photos below show the abundance of pink Harpoon weed Asparagopsis armata, green Sea lettuce Ulvalactuca and new growth of Thong weed Himanthalia elongata and older plants covered in red fuzzy epiphytes. The old wireweed Sargassum muticum plants have died off and the remnants are covered in many epiphytes such as Juicy whorl weed Chylocladia verticilata, Cock’s comb Plocamium cartilagineum and the pretty Iridescent fern weed Osmundea truncata. However, there is new growth everywhere as well so, like Himanthalia, this species seems to have a half-yearly lifecycle. Below some Irish moss Chondrus crispus next to Wireweed. After that, lots of little fuzzy Falkenbergia growing on top of Discoid forkweed Polyides rotundus. This combination grows in a large patch and looks interesting but I struggled to get decent photos, as the dark seaweeds on very white gravel mess up the white balance big time. Next one or two different species of fine flat reds, the last probably Nitophyllum punctatum. The Bushy rainbow wrack Cystoseira tamariscifolia is dying off (here overgrown with Asparagopsis and Dictyota) but the related Bushy berry wrack C. baccata is doing well. Among its epiphytes Spiny straggle weed Gelidium spinosum (ID thanks to Seaweeds of the Atlantic facebook page members) which is also freeliving, and finally the green Codium fragile. One time, when the tide came in, the water was super oxygenated, and all surfaces were covered with small silver bubbles which was beautiful (and annoying as the camera lens was also covered). The following photos show a very different looking Codium fragile, C. tamariscifolia overgrown with Sea beach Delesseria sanguinea and more Thong weed.

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Above an illustration of the decline of seaweeds: Juicy whorl weed Chylocladia verticillata all white and fuzzy (see for a more healthy looking plant this post from 2.5 months ago) on a bed of the common and pretty Discoid fork weed Polyides rotundus. There seem to be around 25 or so (larger) species that are common in these pools. Many of them can be seen in the two photos below (including a stray Bladder wrack, a species that dominates the shore just a meter higher): Below, a whole bunch of individual species. First, Sea beech Delesseria sanguinea, which must have washed up from under the kelp beds (too bad I did not get the entire plant in frame…). Second, a photo of Ulva with Chipolata weed Scytosiphon lomentaria. Third, the brown Divided net weed Dictyota dichotoma. Fourth, Slender wart weed Gracilaria gracilis. Fifth, False eyelash weed Calliblepharis jubata; this plant has grown quite large and has turned from dark red/brown to a much lighter brown. Sixth, the Falkenbergia stage of Harpoon weed Asparagopsis armata (see the third photo) on the right. Seventh, Red grape weed Gastroclonium ovatum. Finally, two photos of my favourite species the blue Bushy rainbow wrack Cystoseira tamariscifolia.

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More seaweed photos, taken a couple of days after the ones in the previous post, when it was overcast and the water was less clear. The photos are not as good, but there are still a lot of interesting species to see. Below some photos showing the diversity of species next and on top of each other. In the last two months, most species have been growing quite a lot. There are quite large patches of Slender-beaded coral weed Jania rubens. Bushy rainbow wrack Cystoseira tamariscifolia plants are completely overgrown with all kinds of epiphytes, seaweeds, sponges and colonial tunicates, and often have a Nursehound egg case attached. Next, photos of individual species. First some flat reds: Leafy rose weed Rhodophyllis divaricata, Beautiful fan weed Callophyllis laciniata, Branched hidden ribs Cryptopleura ramosa (probably), the invasive species Devil’s tongue weed Grateloupia turuturu and Under tongue weed Hypoglossum hypoglossoides. After that, two species that look a bit similar: left the reddish Discoid fork weed Polyides rotundus and right Clawed fork weed Furcellaria lumbricalis. The former is one of the most common species (also on the photo above it) but difficult to photograph as it usually sits on the white sand. After that, Juicy whorl weed Chylocladia verticillata. Last, two quite unassuming species: Black scour weed Ahnfeltia plicata and Sea flax weed Stypocaulon scoparium. Identifications made possible using the must-have Seasearch Guide to Seaweeds of Britain and Ireland, David Fenwick’s excellent aphotomarine website (and personal communication) and the good people of the Seaweeds of the NE Atlantic facebook group (any mistakes are my own).

I have been a bit busy and so the photos below are some weeks old. The seaweeds are in decline already it seems. Actually, that is not true, there are plenty of seaweeds growing, but some of the prettier ones are dying off and some of the uglier ones are taking over. The window to take the nicest rock pool shots is quite short, pretty much early spring only. The ubiquitous False eyelash weed Calliblepharis jubata is yellowing, the green Sea lettuce Ulva lactuca is starting to cover everything and the Red grape weed is getting ‘fluffy’. Not the best session photo quality-wise and probably the last of the year. The Bushy rainbow wrack Cystoseira tamariscifolia is abundant and looking good (on the photo with Discoid forkweed Polyides rotundus) and I managed I nice shot of young Thong (or Spaghetti) weed Himanthalia elongata. I have done some more research into ‘proper’ underwater cameras and was tipped of about the Canon G16 (thanks Thomas from HydroMotion Media), maybe something for next year….The past couple of times when focusing on the seaweeds I also encountered some animals (it is hard not to). Many Snakelocks anemones Anemonia viridis, with some having very short tentacles. Next, a Decorator crab Macropodia rostrata covered in Banded pincer weed Ceramium. Mermaid’s purses (egg cases) of the Bull huss/Greater-spotted Dogfish/Large-spotted Catshark/Nursehound Scyliorhinus stellaris seem to be exclusively attached to Bushy rainbow wrack. Finally, a Stalked jellyfish Haliclystus octoradiatus on Wireweed Sargassum muticum.

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Another couple of sessions trying to take seaweed photo’s. A couple of seaweed species are really thriving at the moment, one is False eyelash weed Calliblepharis jubata in the middle of the picture above. In the picture below a couple of other species, Irish moss Chondrus crispus in the foreground, Discoid forkweed Polyides rotundus on the left, Black scourweed Ahnfeltia plicata on the right, with some Red grape weed Gastroclonium ovatum at the top. Below that two ‘miscellanious’ pictures and after that some photos of individual species: the photo that turned out best was of Bonnemaison’s hook weed Bonnemaisonia hamifera, an invasive species from the Pacific. After that Juicy whorl weed Chylocladia verticilliata, a Plocamium species and my favourite, the Bushy rainbow wrack Cystoseira tamariscifolia.

This friday, I tried my hand at some more underwater rock pool photography with my point-and-shoot Canon Powershot (see also here and here). This is both rewarding as the colours of seaweeds are so vivid and the textures so varied, and frustrating, as I cannot use the viewfinder and even if I could, lots of shots would be much better using a wider-angle lens. Also, I am often kicking up silt with my wellies and the nicest shots often are just out of reach. So next time, I should really photograph whilst snorkelling. (It would be great to use an SLR in an underwaterhousing. I bought a much cheaper and much more cumbersome ‘underwater-camera bag‘ without remembering that my old, not-so-frequently-used-anymore Canon EOS 400D does not have a viewfinder. I am afraid this will make the experience less, not more, fun…) Anyway, the trick for now is to take many pics and hope some turn out all right. I like the ones with a water surface reflection best. The nicest one was a snakelocks anemone among corraline algae. Next, what is may or may not be Sea flax weed Stypocaulon scoparium. After that, the brown Divided net weed Dictyota dichotoma growing inbetween Discoid fork weed Polyides rotundus, a Bull huss/Nursehound/Large-spotted dogfish Scyliorhinus stellaris mermaid’s purse and a Spiny starfish Marthasterias glacialis. Probably more photos soon as the pools look by far the best in early spring.

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During this spring and summer I have taken my Canon Powershot 130D to the shore in addition to my iPhone. I have been trying to take underwater pictures of seaweeds with it, which is a bit of a challenge as (when you are not snorkelling) you usually have to take the photos ‘blind’. Some of ’em however turned out quite nice, here is a selection.I still find it hard to identify species. Here are some I do know. First, Hairy sand weed Cladostephus spongiosus. Second, a pool with many reds, in the foreground Discoid forkweed Polyides rotundus. Third, the invasive species Grateloupia turuturu. The big plants bleached and died off in summer but the young ones are growing already. Fourth, (probably) Sea flax weed Stypocaulon scoparium. I will post some more pics soon.